This property was meant to be translatable, as the comment on the line before indicates. It'll allow translators to manually toggle whether the buttons in the omnibar should he homogeonous, because in certain languages it takes a really big width which means that the different labels in the popover and buttons are spread in long distances.
So this commit makes it translatable.
Normally it should be correctly translatable, since it's just yet an other property and the thing that extracts gettext strings doesn't know if it's right or not to translate it.